1-Hexene Isomerization Over Nano-crystalline Zeolite Beta: Effects of Metal and Carrier Gases on Catalytic Performance

Zeolite Beta crystals in nanometer size (about 44 nm) were hydrothermally synthesized and its catalytic activities with and without Pt impregnation were studied for 1-hexene isomerization in presence of different carrier gases, namely, hydrogen, nitrogen and carbon dioxide and also in the absence of carrier gas at reaction temperatures of 473–573 K and 0.1 MPa. General observation for all the cases was that with reaction temperature, hexene conversion increased, however, total isomer selectivity dropped. With temperature skeletal isomerization increased at the cost of double bond shift isomerization. Observed product distribution has been explained on the basis of zeolite structure and crystal size. Catalyst performed better in nitrogen than in hydrogen or carbon dioxide as carrier gas. Nevertheless, catalyst life was shorter with nitrogen as carrier gas than that with hydrogen.     

Crystallization Kinetics and Mechanism of Low-Expansion Lithium Aluminosilicate Glass-Ceramics by Dilatometry

The crystallization kinetics and mechanism of a precursor glass of lithium aluminosilicate (LAS)-based commercial low-expansion glass-ceramics were investigated using a dilatometer. The isothermal crystallization behavior of β-quartz solid solution (ss) was found to obey the Avrami equation. Nonisothermal crystallization data were analyzed by the Ozawa method and modified Kissinger equation. The value of the Avrami exponent ( n ) was ∼1.5, and the apparent activation energy ( E _a) was ∼500 kJ/mol, which was close to that of the diffusion of silicon and aluminum ions as well as metal–oxygen bond strengths, suggesting a three-dimensional (3D) diffusion-controlled reaction mechanism.     

An estimation of S/N degradation at millimeter waves during rain events

The use of Ka Band (20/30 GHz) for future satellite communications has been addressed. The exploitation of Ka band with a bandwidth of 2500 MHz seems to represent the largest significant achievement in satellite communications potential, so far. The problems associated with the use of this frequency band such as attenuation and receiver noise temperature (floor) variation with rain has been addressed. The receiver noise floor variation with rain has so far been ignored. Therefore, in view of propagation and noise study over this Ka Band, both signal attenuation and receiver noise floor variations with rain rate are estimated using dual frequency radiometers operating at 22.235 and 31.4 GHz over a tropical station, Calcutta, India.     

Radiometric Measurements of Rain Attenuation at 22.2 and 31.4 GHz Over Calcutta

Measurements of rain attenuation over Calcutta have been made using radiometers operating at frequencies of 22.235 and 31.4 GHz. The results have been correlated with observations of rainfall rates made with a fast-response rain gauge. The distributions of peak rain rates over Calcutta for two different years and the cumulative occurrences of rainfall rates and attenuations at the two frequencies are presented.     

Studies in swelling of cotton. I. Neutral salt technique to determine the true swelling parameters in cadoxen

This paper describes the swelling of cotton fiber in cadoxen containing 4.6% cadmium (w/w) and 30% ethylenediamine (w/w). A special neutral salt technique is described involving the analysis of extract as well as mother liquor which enables the determination of mechanically held liquor and hence the values of true absorption. The percentage true weight swelling values are much lower than the percentage apparent weight swelling as measured by centrifuge technique. The effect of variation in material-to-liquor ratio on the true absorption of cadmium and ethylenediamine is also investigated.     

Effect of testing conditions and microstructure on the sliding wear of graphite fibre/PEEK matrix composites

The sliding friction and wear behaviour of unreinforced polyetheretherketone (PEEK) matrix and its unidirectional continuous and two-dimensional woven graphite fibre-reinforced composites were investigated. The operating wear mechanisms, as evinced by scanning electron microscopy of the worn surfaces, and the coefficients of friction and the wear rates changed considerably with the fibre reinforcement form and orientation. Sliding wear rates, on account of their extreme sensitivity to the microstructure of the interacting surfaces at the sliding interface, were found to be a function of not only the surface roughness, but also of the sliding time. Complex interactions arising due to the effects of the testing parameters such as fibre orientation, sliding velocity, contact pressure and interface temperature were characterized for the neat matrix and the two composite systems. The wear rates of the two-dimensional woven composites were almost an order of magnitude lower than those of the unidirectional fibre composite or the unreinforced matrix.     

Oblique flexural gravity-wave scattering due to changes in bottom topography

Oblique flexural gravity-wave scattering due to an abrupt change in water depth in the presence of a compressive force is investigated based on the linearized water-wave theory in the case of finite water depth and shallow-water approximation. Using the results for a single step, wide-spacing approximation is used to analyze wave transformation by multiple steps and submerged block. An energy relation for oblique flexural gravity-wave scattering due to a change in bottom topography is derived using the argument of wave energy flux and is used to check the accuracy of the computation. The changes in water depth significantly contribute to the change in the scattering coefficients. In the case of oblique wave scattering, critical angles are observed in certain cases. Further, a resonating pattern in the reflection coefficients is observed due to change in the water depth irrespective of the presence of a compressive force in the case of a submerged block.     

Determination of iodide and iodate in edible salt by ion chromatography with integrated amperometric detection

Iodised salt compositions formulated with potassium iodate typically have iodate content of 20–40 ppm (μg/g) which translates to iodine content of 15–30 ppm. The technique of iodide estimation in brine by ion chromatography with amperometric detection was applied to iodate estimation in salt. The method involved reduction of iodate to iodide with excess sodium bisulphite followed by estimation of iodide. No other pre-treatment was necessary for iodate estimation in the concentration range of interest for iodised salt. Quantitative analysis was feasible for iodate concentrations ?5 ppm in salt. Iodised salt formulations containing iodide and iodate together were also analysed and the two constituents were quantified separately. Interferences from impurities normally present in salt were insignificant. An important advantage of the present method is that it eliminates the possibility of misleading results from potential adulterants which can impart positive iodometric test while, at the same time, keeping the analytical procedure simple.     

Study on growth of hollow nanoparticles of alumina

This article addresses the growth of hollow nanocrystalline particles of γ-alumina by the post-oxidation of nano-aluminium particles in air. The nanoparticles of aluminium were synthesized in a DC-transferred arc thermal plasma reactor. The as-synthesized nano-aluminium particles were oxidized, in air, at different temperatures. The as-synthesized parent nano aluminium and their daughter nanoparticles of aluminium oxide were thoroughly characterized with the help of X-ray diffraction analysis, high resolution transmission electron microscopy and thermogravimetric analysis. Two-step oxidation behaviours, unique in nanoparticles, are found to be the main driving force behind the formation of hollow spherical structures. The entire phenomenon is compared with the oxidation behaviour of coarse grain aluminium. The content of γ-alumina, identified by X-ray diffraction, relative to that of unreacted aluminium, has increased almost exponentially with the oxidation temperature in the case of nano aluminium. Similar behaviour is not observed in the case of coarse grain aluminium. The crystalline features of alumina, forming the walls of the hollow sphere, were confirmed by high resolution transmission electron microscopy.     

RFID Transponders

adio frequency identification (RFID) or auto-identification (ID) is a contactless data transmission and reception technique between the data carrying device, called a transmitter responder (transponder) or an RFID tag, and an interrogator, which is also known as an RFID reader. A more abstract approach to defining Auto-ID reveals that Auto-ID involves the automated extraction of the identity of an object [1], [2]. The contactless ID system relies on data transmission via radio frequency electromagnetic (EM) signals, and consequently, the whole operation is line-of-sight and weather independent [3]. These advantages overcome the limitations of optical barcodes, which are line-of-sight and weather dependent and need manual operation.